As law enforcement doubles down with its effort to gain access to encrypted communications for the sake of national security, new questions emerge following an apparent failure to parse evidence that’s already publicly available.

Recent attacks in San Bernardino and Paris have rekindled calls from law enforcement officials in the United States and abroad for tech companies to ensure authorities aren’t left in the dark when it comes to collecting evidence.

Authorities said the problem has become increasingly apparent in recent months as more and more corporations, from Apple to Google, put out products that allow consumers to communicate with end-to-end encryption and, if implemented properly, under the radar of eavesdroppers, state-sanctioned or other.

Yet while efforts to give government agencies the ability to break encryption have been ramped up in the wake of those terror attacks, at least one expert now claims that authorities are fumbling with evidence that needn’t be cracked.

Rita Katz has spent nearly 20 years tracking, studying and reporting on terror groups, and currently leads the SITE Intelligence Group, a Bethesda-based company that monitors the online activity of groups ranging from white supremacists to jihadi sects. In an op-ed in The Washington Post this week, Ms. Katz said her group had warned officials a week before two American men attempted to storm an event in Garland, Texas, earlier this year after seeing calls for action posted on Twitter by supporters of the Islamic State group.

“The Garland, Tex., shooting — the only example [FBI Director James] Comey used as an impetus to regulate encrypted technology — in fact makes the opposite point. Attacker Elton Simpson, who was under previous FBI terror-related investigations, used Twitter to openly follow and communicate with high-profile terrorists,” Ms. Katz wrote.

Simpson, who was killed by police along with co-assailant Nadir Soofi while attempting to breach a “Muhammad Art Exhibit,” had maintained a Twitter account that was followed by English-speaking supporters of the Islamic State, including Junaid Hussain, a British-born computer hacker who was killed by a U.S. airstrike earlier this year, and Mohamed Abdullahi Hassan, a known American jihadist.

Hassan had encouraged people over Twitter to attack the May 3 art show in Garland, the SITE director wrote, through posts that were retweeted by Simpson.

“We at SITE, using only open-source information, reported on the call before the attack took place, and the FBI had a week to investigate the matter before the shooting. Though only nine Twitter users retweeted the call for attack, the FBI failed to prevent it,” she wrote.

On the SITE website, the anti-jihadi group reported on April 27 that “Jihadists on Twitter circulated calls and insinuations for attacks on cartoonists in Australia and America for past and planned depictions of the Prophet.”

“The encrypted messages Comey mentioned before the Judiciary Committee were discovered by the FBI only after the attack took place, but Simpson’s open-source communication was available far in advance. There is in fact no evidence that this or any of these other lone-wolf attacks could have been prevented by regulation of encryption technology,” Ms. Katz added.

Nevertheless, efforts to ensure communication platforms are equipped with so-called “backdoors” for investigators have increased in the wake of the recent attacks, with President Obama pledging earlier this month to “urge high-tech and law enforcement leaders to make it harder for terrorists to use technology to escape from justice.”

Writing for The Post, however, Ms. Katz said that jihadists’ main tool for planning and executing attacks hasn’t been encrypted messaging platform, but social media that can be easily scoured by investigators.

Indeed, the Justice Department announced this week it had charged a Pennsylvania teenager and obtained a guilty plea from a pizza shop owner from New York, both of whom had landed in hot water supposedly aiding the Islamic State through social media — only a fraction of the dozens of people arrested in the U.S. in recent months for ties to the group also known as ISIS.

“Once you start using Twitter, you start to understand how powerful it is, and that is why ISIS is taking advantage of it,” Ms. Katz told The Post previously. “Twitter must understand that they have to be responsible for the kind of information that they disseminate.”

Senate Intelligence Committee Chairwoman Dianne Feinstein, California Democrat, said earlier this month that she will seek legislation that would allow investigators to “pierce” encryption, but Rep. Jim Langevin, a Rhode Island Democrat and co-chair of the House Cybersecurity Caucus, told Politico this week that’s he didn’t think there was “any appetite in Congress right now” for such a bill.

Social media, on the other hand, is a different story — on Wednesday this week, the House passed a bill that would force the White House to put together a comprehensive strategy with regards to disrupting terrorist organizations’ social media use and online radicalization efforts.

“When it comes to the external message, our message is being trumped by ISIS,” Rep. Brad Sherman, California Democrat, said during an earlier hearing in support of the bill. “We are losing a popularity contest to people who behead women.”